Check if we are on ipv4, ipv6 or dualStack when doing tailscale

pkg/agent/config/config.go

@@ -390,15 +390,24 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 		if err != nil {
 			return nil, err
 		}
-		if len(vpnInfo.IPs) != 0 {
-			logrus.Infof("Node-ip changed to %v due to VPN", vpnInfo.IPs)
+
+		var vpnIPs []net.IP
+		if vpnInfo.IPv4Address != nil {
+			vpnIPs = append(vpnIPs, vpnInfo.IPv4Address)
+		}
+		if vpnInfo.IPv6Address != nil {
+			vpnIPs = append(vpnIPs, vpnInfo.IPv6Address)
+		}
+
+		if len(vpnIPs) != 0 {
+			logrus.Infof("Node-ip changed to %v due to VPN", vpnIPs)
 			if len(envInfo.NodeIP) != 0 {
 				logrus.Warn("VPN provider overrides configured node-ip parameter")
 			}
 			if len(envInfo.NodeExternalIP) != 0 {
 				logrus.Warn("VPN provider overrides node-external-ip parameter")
 			}
-			nodeIPs = vpnInfo.IPs
+			nodeIPs = vpnIPs
 			flannelIface, err = net.InterfaceByName(vpnInfo.VPNInterface)
 			if err != nil {
 				return nil, errors.Wrapf(err, "unable to find vpn interface: %s", vpnInfo.VPNInterface)

pkg/cli/server/server.go

@@ -228,12 +228,27 @@ func run(app *cli.Context, cfg *cmds.Server, leaderControllers server.CustomCont
 		if err != nil {
 			return err
 		}
-		if len(vpnInfo.IPs) != 0 {
-			logrus.Infof("Advertise-address changed to %v due to VPN", vpnInfo.IPs)
-			if serverConfig.ControlConfig.AdvertiseIP != "" {
-				logrus.Warn("Conflict in the config detected. VPN integration overwrites advertise-address but the config is setting the advertise-address parameter")
+		// If we are in ipv6-only mode, we should pass the ipv6 address. Otherwise, ipv4
+		if utilsnet.IsIPv6CIDRString(util.JoinIPNets(serverConfig.ControlConfig.ClusterIPRanges)) {
+			if vpnInfo.IPv6Address != nil {
+				logrus.Infof("Advertise-address changed to %v due to VPN", vpnInfo.IPv6Address)
+				if serverConfig.ControlConfig.AdvertiseIP != "" {
+					logrus.Warn("Conflict in the config detected. VPN integration overwrites advertise-address but the config is setting the advertise-address parameter")
+				}
+				serverConfig.ControlConfig.AdvertiseIP = vpnInfo.IPv6Address.String()
+			} else {
+				return errors.New("tailscale does not provide an ipv6 address")
+			}
+		} else {
+			if vpnInfo.IPv4Address != nil {
+				logrus.Infof("Advertise-address changed to %v due to VPN", vpnInfo.IPv4Address)
+				if serverConfig.ControlConfig.AdvertiseIP != "" {
+					logrus.Warn("Conflict in the config detected. VPN integration overwrites advertise-address but the config is setting the advertise-address parameter")
+				}
+				serverConfig.ControlConfig.AdvertiseIP = vpnInfo.IPv4Address.String()
+			} else {
+				return errors.New("tailscale does not provide an ipv4 address")
 			}
-			serverConfig.ControlConfig.AdvertiseIP = vpnInfo.IPs[0].String()
 		}
 		logrus.Warn("Etcd IP (PrivateIP) remains the local IP. Running etcd traffic over VPN is not recommended due to performance issues")
 	} else {

pkg/util/net.go

@@ -10,6 +10,7 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
 	apinet "k8s.io/apimachinery/pkg/util/net"
+	netutils "k8s.io/utils/net"
 )
 
 // JoinIPs stringifies and joins a list of IP addresses with commas.
@@ -85,10 +86,9 @@ func JoinIP4Nets(elems []*net.IPNet) string {
 // If no IPv6 addresses are found, an error is raised.
 func GetFirst6(elems []net.IP) (net.IP, error) {
 	for _, elem := range elems {
-		if elem == nil || elem.To16() == nil {
-			continue
+		if elem != nil && netutils.IsIPv6(elem) {
+			return elem, nil
 		}
-		return elem, nil
 	}
 	return nil, errors.New("no IPv6 address found")
 }
@@ -97,10 +97,9 @@ func GetFirst6(elems []net.IP) (net.IP, error) {
 // If no IPv6 addresses are found, an error is raised.
 func GetFirst6Net(elems []*net.IPNet) (*net.IPNet, error) {
 	for _, elem := range elems {
-		if elem == nil || elem.IP.To16() == nil {
-			continue
+		if elem != nil && netutils.IsIPv6(elem.IP) {
+			return elem, nil
 		}
-		return elem, nil
 	}
 	return nil, errors.New("no IPv6 CIDRs found")
 }
@@ -125,7 +124,7 @@ func GetFirst6String(elems []string) (string, error) {
 func JoinIP6Nets(elems []*net.IPNet) string {
 	var strs []string
 	for _, elem := range elems {
-		if elem != nil && elem.IP.To4() == nil {
+		if elem != nil && netutils.IsIPv6(elem.IP) {
 			strs = append(strs, elem.String())
 		}
 	}

pkg/vpn/vpn.go

@@ -22,7 +22,8 @@ type TailscaleOutput struct {
 
 // VPNInfo includes node information of the VPN. It is a general struct in case we want to add more vpn integrations
 type VPNInfo struct {
-	IPs          []net.IP
+	IPv4Address  net.IP
+	IPv6Address  net.IP
 	NodeID       string
 	ProviderName string
 	VPNInterface string
@@ -112,15 +113,14 @@ func getTailscaleInfo() (VPNInfo, error) {
 	logrus.Debugf("Output from tailscale status --json: %v", output)
 
 	var tailscaleOutput TailscaleOutput
-	var internalIPs []net.IP
 	err = json.Unmarshal([]byte(output), &tailscaleOutput)
 	if err != nil {
 		return VPNInfo{}, fmt.Errorf("failed to unmarshal tailscale output: %v", err)
 	}
 
-	for _, address := range tailscaleOutput.TailscaleIPs {
-		internalIPs = append(internalIPs, net.ParseIP(address))
-	}
+	// Errors are ignored because the interface might not have ipv4 or ipv6 addresses (that's the only possible error)
+	ipv4Address, _ := util.GetFirst4String(tailscaleOutput.TailscaleIPs)
+	ipv6Address, _ := util.GetFirst6String(tailscaleOutput.TailscaleIPs)
 
-	return VPNInfo{IPs: internalIPs, NodeID: "", ProviderName: "tailscale", VPNInterface: tailscaleIf}, nil
+	return VPNInfo{IPv4Address: net.ParseIP(ipv4Address), IPv6Address: net.ParseIP(ipv6Address), NodeID: "", ProviderName: "tailscale", VPNInterface: tailscaleIf}, nil
 }